Sierra Space's Dream Chaser Checks off a Major Milestone

The first Dream Chaser spacecraft slated to go into orbit has completed its assembly and is being readied for shipment to NASA in Ohio for a series of tests.   

Within a few weeks, the Dream Chaser spaceplane, named "Tenacity" and carrying the serial number DC-101, will be out the door on the way to a NASA facility in Ohio for a battery of tests to prove it can survive the rigors of spaceflight.

When I say "completed" you might want to consider that it doesn't necessarily mean "flight ready."  For the series of tests it's going to go through, access to some points that are covered for flight is necessary, so some covers and tiles are missing 

A collage of four photos of Tenacity in Sierra Space's Colorado factory.  Image credit: Stephen Clark/Ars Technica

“We’re almost done with everything," said Angie Wise, Sierra Space's chief safety officer. "We’re finishing all the closeout panels. We’re essentially getting it ready for shipping. We’ve checked out the landing gear. We’re going to put everything back in, stow it, and then move it onto the (transport) fixture and get it out of here.”

While very reminiscent of the Space Shuttles, it isn't a copy of the STS platform.

Dream Chaser is about a quarter of the size of a space shuttle orbiter, with roughly half of the shuttle's habitable volume. It's about 30 feet (9 meters) long, with a wingspan of 23 feet (7 meters). Those wings fold up, like the wings of a fighter jet on an aircraft carrier, to fit inside the payload envelope of its rocket. The first Dream Chaser missions will lift off on United Launch Alliance Vulcan rockets from Cape Canaveral, Florida, but Sierra Space says its spaceplane can fly on different launch vehicles.

At this point, with Vulcan's first flight scheduled for this Christmas Eve, it seems the launch of Tenacity might be in the December of '24 time frame. 

Sierra Space's vision is to change the way we go to orbit and especially how we come back.  Like the Shuttles, Dream Chasers will land on a runway.  A design feature is that reentry should be easy on the people or payloads taking the ride.  The flight plan is to limit deceleration to no more than 1.5 Gs.  

Unlike the shuttles, SpaceX's Cargo Dragon or Northrup Grumman's Cygnus, Dream Chasers are neither fully reusable or fully disposable. The Dream Chaser itself is designed for 15 flights, but they will fly with a detachable cargo module that's disposable. 

This pressurized cargo pod, named "Shooting Star," has solar arrays that will unfurl in orbit to generate power. It's attached to the rear of Dream Chaser and will be the connecting point between the spaceplane and the International Space Station.

With the Shooting Star attached, Tenacity can carry 12,000 pounds to the space station; giving up Shooting Star for the return drops the payload that can be brought back down to about 4,000 pounds.  The Shooting Star will be used to dispose of garbage from the ISS, incinerating during reentry.  

Originally intended to fly in 2019, Sierra Space is very late.  The problem started out due to "supply chain" issues, which gave Sierra a strong incentive to do as much of their own parts manufacturing as possible.  One of the interesting impacts of that is that Dream Chaser has a unique propulsion system. 

The spacecraft has 26 small rocket engines, each capable of operating at three discrete levels of thrust for fine control or more significant orbit adjustments. Uniquely in the space industry, these thrusters consume a mix of kerosene and hydrogen peroxide propellants rather than toxic hypergolic propellants that ignite on contact with one another.

"We wanted to have a fuel system that was green instead of using hypergolics, so we could land it on a runway and we could walk up to the vehicle without being in hazmat suits," Vice said. "That was hard, I have to say."

On October 24, Sierra Space moved the Shooting Star cargo module into position behind the Dream Chaser spaceplane for checkouts before shipment to Ohio for environmental testing. Image credit: Shay Saldana/Sierra Space.

Dream Chaser's next stop after leaving Sierra Space's factory will be NASA's Neil Armstrong Test Facility in Ohio, formerly known as Plum Brook Station. The spacecraft will travel by road from Colorado, but Sierra Space is keeping its route and shipment date secret for security reasons. Wise said the spacecraft will stay at the Ohio test facility for one to three months, depending on how the testing goes.

The disposable cargo module for the first Dream Chaser flight to the space station has already departed Sierra Space's factory for Ohio. Once the Tenacity spaceplane arrives there, ground teams will connect the two segments of the Dream Chaser cargo freighter and run them through integrated tests. Those will include vibration and acoustic tests to check that the spacecraft can withstand the shaking and sound of a rocket launch. Sierra Space will also place the spacecraft inside a giant thermal vacuum chamber.

Thermal testing will be part of the process with the vibration and acoustic tests, too - what we used to call, "shake and bake" back in my days doing that. 

This summary just barely touches on a lot of the interesting details in the piece on Ars Technica.  Worth a read if you find the Dream Chaser interesting.